In the first Foundation novel, the science fiction writer Isaac Asimov imagined an expert whose particular skill was applying symbolic logic to human speech and documents in order to boil their statements down to the barest and clearest essentials. Five days' worth of discussions with a particularly clever politician were, by this method, boiled down to absolutely nothing: everything he said cancelled itself out. Without, it has to be said, anyone's noticing in real time.

Asimov was writing in 1951. Sixty years later we have a cruder, but simpler, automated method of achieving more or less the same thing, called the "word cloud". Essentially, a bit of software goes through any type of electronic text and creates a statistical analysis of the words that appear in it. The software then creates a visual display using font sizes and colours to show at a glance which words appear most frequently. Geeks love this kind of thing, not least because word clouds sometimes show us obsessions we didn't know we had.

David McCandless, who specialises in visualising data, decided to apply this technique to the sun-sign horoscopes that appear on Yahoo! He and his team painstakingly scraped more than 22,000 horoscopes off the site, eliminated those targeted at specific groups (for example, teens) or types of questions (for example, career advice). The result, Horoscoped, is a set of word clouds for each of the 12 traditional star signs. The bottom line: note how, sign after sign, the same words dominate the landscape. Feel. Sure. Keep. Love.

Of course, sceptics have long maintained that your average mass-media sun-sign horoscope is a collection of meaningless banalities, an assessment with which many "serious" astrologers – that is, astrologers who do personal charts incorporating planetary movements – say they agree. Basically, mass-media sun-sign astrology is to pop psychology what Muzak is to easy listening. What McCandless shows here is that it isn't just prejudice to characterise these horoscopes as a triumph of the blandly reassuring.

Various experiments have shown this over the years. In one experiment, people were asked to pick their horoscope out of a basket of sun-sign predictions and failed. In another, the experimenters supplied birth data to several astrologers and sent the resulting horoscopes to subjects who supplied their own birth data – and who rated the accuracy of those horoscopes quite highly. In fact, of course, the birth information originally supplied to the astrologers was that of a notorious mass murderer. And so on.

My favourite was the experiment in which three groups of people were told variously that they were reading: 1) a personality description generally true of most people; 2) the horoscope for their sun sign; 3) a personal horoscope drawn up just for them by an astrologer based on their birth date, time and place. The bottom line: the more personal people believed the passage to be, the more highly they rated its accuracy. In all cases they were given the same passage to read.

But, of course, that only works as long as the horoscope contains nothing that might alienate the subject – which means that blandness and universal applicability are the keys to success. You win readers/subjects by giving them a sufficiently blank description that they can project themselves into it. And as long as you don't lose them by showing them anything they wouldn't like to think about themselves, you're golden. What McCandless has achieved is to winkle out the precise formula for becoming a successful astrologer. Feel. Love. Keep. Sure.